Fluorination of sulfide minerals with ammonium hydrogen difluoride

The fluorination reactions of natural sulfides with ammonium hydrogen difluoride (NH4HF2) were studied. It was established that nonstoichiometric ammonium fluoroferrates are formed by interaction of pyrrhotite with NH4HF2. Their composition depends on the access of oxygen. Fe(II) is responsible for the formation of fluoride perovskites and Fe(III) gives elpasolites. The process is accompanied by formation of elementary sulfur. Close to stoichiometry sulfide minerals such as sphalerite ZnS, galenite PbS, pyrite FeS2, troilite FeS, chalcopyrite CuFeS2, arsenopyrite FeAsS, molybdenite MoS2 do not interact with ammonium hydrogen difluoride.